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Ice Flow Across A Warm-Based/Cold-Based Transition At A Glacier Margin, Peter Lindsay Moore, Neal R. Iverson, Denis Cohen 2015 Iowa State University

Ice Flow Across A Warm-Based/Cold-Based Transition At A Glacier Margin, Peter Lindsay Moore, Neal R. Iverson, Denis Cohen

Peter Lindsay Moore

Where polythermal glaciers have frozen margins that buttress otherwise temperate-based sliding ice, longitudinal compression can strongly influence ice flow trajectory, and consequently sediment transport paths. Past efforts to model flow in the vicinity of a basal thermal transition (BTT) have generally relied on simplified boundary conditions or rheological idealizations, making these model results difficult to apply to real glacier termini. Herein, we present results of numerical simulations using a power-law rheology and with boundary conditions that better represent the frozen margin. Model results indicate that a transition to a non-sliding frozen margin causes a decline in surface velocity made possible ...


Effect Of A Cold Margin On Ice Flow At The Terminus Of Storglacïaren, Sweden: Implications For Sediment Transport, Peter Lindsay Moore, Neal R. Iverson, Keith A. Brugger, Denis Cohen, Thomas S. Hooyer, Peter Jansson 2015 Iowa State University

Effect Of A Cold Margin On Ice Flow At The Terminus Of Storglacïaren, Sweden: Implications For Sediment Transport, Peter Lindsay Moore, Neal R. Iverson, Keith A. Brugger, Denis Cohen, Thomas S. Hooyer, Peter Jansson

Peter Lindsay Moore

The cold-based termini of polythermal glaciers are usually assumed to adhere strongly to an immobile substrate and thereby supply significant resistance to the flow of warm-based ice upglacier. This compressive environment is commonly thought to uplift basal sediment to the surface of the glacier by folding and thrust faulting. We present model and field evidence from the terminus of Storglacïaren, Sweden, showing that the cold margin provides limited resistance to flow from up-glacier. Ice temperatures indicate that basal freezing occurs in this zone at 10–1 – 10–2 ma–1, but model results indicate that basal motion at rates greater ...


Debris-Bed Friction Of Hard-Bedded Glaciers, Denis Cohen, Neal R. Iverson, T. S. Hooyer, U. H. Fischer, M. Jackson, Peter Lindsay Moore 2015 Iowa State University

Debris-Bed Friction Of Hard-Bedded Glaciers, Denis Cohen, Neal R. Iverson, T. S. Hooyer, U. H. Fischer, M. Jackson, Peter Lindsay Moore

Peter Lindsay Moore

Field measurements of debris-bed friction on a smooth rock tablet at the bed of Engabreen, a hard-bedded, temperate glacier in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction of up to 500 kPa. The corresponding bulk friction coefficient between the dirty basal ice and the tablet was between 0.05 and 0.08. A model of friction in which nonrotating spherical rock particles are held in frictional contact with the bed by bed-normal ice flow can account for these measurements if the power law exponent for ice flowing past large clasts is 1 ...


Deformation Of Debris-Ice Mixtures, Peter Lindsay Moore 2015 Iowa State University

Deformation Of Debris-Ice Mixtures, Peter Lindsay Moore

Peter Lindsay Moore

Mixtures of rock debris and ice are common in high-latitude and high-altitude environments and are thought to be widespread elsewhere in our solar system. In the form of permafrost soils, glaciers, and rock glaciers, these debris-ice mixtures are often not static but slide and creep, generating many of the landforms and landscapes associated with the cryosphere. In this review, a broad range of field observations, theory, and experimental work relevant to the mechanical interactions between ice and rock debris are evaluated, with emphasis on the temperature and stress regimes common in terrestrial surface and near-surface environments. The first-order variables governing ...


Conditions For Thrust Faulting In A Glacier, Peter Lindsay Moore, Neal R. Iverson, Denis Cohen 2015 Iowa State University

Conditions For Thrust Faulting In A Glacier, Peter Lindsay Moore, Neal R. Iverson, Denis Cohen

Peter Lindsay Moore

Dipping, arcuate bands of debris-rich ice outcropping near the margins of glaciers are often interpreted as thrust faults, assumed to originate in zones of longitudinal compression. Identification of thrusts is typically based either on the geometry and sedimentology of the debris bands or on the crystal fabric of surrounding ice, but the physical processes necessary to generate thrusts are rarely evaluated. Herein, we combine a numerical model of compressive ice flow near a glacier margin with theoretical stress and strain rate criteria for ice fracture and stress criteria for frictional slip to determine the conditions necessary for thrust faulting in ...


Using Pressure Pulse Seismology To Examine Basal Criticality And The Influence Of Sticky Spots On Glacial Flow, J. L. Kavanaugh, Peter Lindsay Moore, C. F. Dow, J. W. Sanders 2015 University of Alberta

Using Pressure Pulse Seismology To Examine Basal Criticality And The Influence Of Sticky Spots On Glacial Flow, J. L. Kavanaugh, Peter Lindsay Moore, C. F. Dow, J. W. Sanders

Peter Lindsay Moore

Here we report results of water pressure pulse studies conducted at Storglaciären (Sweden) and West Washmawapta Glacier (British Columbia, Canada). Comparison of pressure pulse records with meteorological conditions at Storglaciären indicates that several periods of increased basal slip activity observed during a 10 day interval of summer 2008 were due to precipitation loading of the glacier surface, rather than to infiltration of surface water to the glacier bed; this indicates that the glacier bed was close to the failure strength for much of this interval. Pressure pulse magnitudes for the two glaciers were well-fit by power law distributions similar to ...


Effect Of A Cold Margin On Ice Flow At The Terminus Of Storglaciaren, Sweden: Implications For Sediment Transfer, Keith A. Brugger, Peter L. Moore, Neal R. Iverson, Denis Cohen, Thomas S. Hooyer, Peter Jansson 2015 University of Minnesota, Morris

Effect Of A Cold Margin On Ice Flow At The Terminus Of Storglaciaren, Sweden: Implications For Sediment Transfer, Keith A. Brugger, Peter L. Moore, Neal R. Iverson, Denis Cohen, Thomas S. Hooyer, Peter Jansson

Peter Lindsay Moore

The cold-based termini of polythermal glaciers are usually assumed to adhere strongly to an immobile substrate and thereby supply significant resistance to the flow of warm-based ice upglacier. This compressive environment is commonly thought to uplift basal sediment to the surface of the glacier by folding and thrust faulting. We present model and field evidence from the terminus of Storglaciaren, Sweden, showing that the cold margin provides limited resistance to flow from up-glacier. Ice temperatures indicate that basal freezing occurs in this zone at 10−1 –10−2 ma−1, but model results indicate that basal motion at rates greater ...


Reply To "Comment On ‘Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa,’ By Jeffrey P. Schaffer”, Richard A. Becker, Basil Tikoff, Paul R. Riley, Neal R. Iverson 2015 University of Wisconsin-Madison

Reply To "Comment On ‘Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa,’ By Jeffrey P. Schaffer”, Richard A. Becker, Basil Tikoff, Paul R. Riley, Neal R. Iverson

Geological and Atmospheric Sciences Publications

No abstract provided.


Heat Sources Within The Greenland Ice Sheet: Dissipation, Temperate Paleo-Firn And Cryo-Hydrologic Warming, M. P. Lüthi, C. Ryser, L. C. Andrews, G. A. Catania, M. Funk, R. L. Hawley 2015 Laboratory of Hydraulics, Hydrology and Glaciology (VAW)

Heat Sources Within The Greenland Ice Sheet: Dissipation, Temperate Paleo-Firn And Cryo-Hydrologic Warming, M. P. Lüthi, C. Ryser, L. C. Andrews, G. A. Catania, M. Funk, R. L. Hawley

Open Dartmouth: Faculty Open Access Articles

Ice temperature profiles from the Greenland Ice Sheet contain information on the deformation history, past climates and recent warming. We present full-depth temperature profiles from two drill sites on a flow line passing through Swiss Camp, West Greenland. Numerical modeling reveals that ice temperatures are considerably higher than would be expected from heat diffusion and dissipation alone. The possible causes for this extra heat are evaluated using a Lagrangian heat flow model. The model results reveal that the observations can be explained with a combination of different processes: enhanced dissipation (strain heating) in ice-age ice, temperate paleo-firn, and cryo-hydrologic warming ...


Collaborative Research: Byrd Glacier Flow Dynamics, Gordon S. Hamilton 2015 Principal Investigator; University of Maine, Orono

Collaborative Research: Byrd Glacier Flow Dynamics, Gordon S. Hamilton

University of Maine Office of Research and Sponsored Programs: Grant Reports

This award supports a project to understand the flow dynamics of large, fast-moving outlet glaciers that drain the East Antarctic Ice Sheet. The project includes an integrated field, remote sensing and modeling study of Byrd Glacier which is a major pathway for the discharge of mass from the East Antarctic Ice Sheet (EAIS) to the ocean. Recent work has shown that the glacier can undergo short-lived but significant changes in flow speed in response to perturbations in its boundary conditions. Because outlet glacier speeds exert a major control on ice sheet mass balance and modulate the ice sheet contribution to ...


Collaborative Research: Glacier-Ocean Coupling In A Large East Greenland Fjord, Gordon S. Hamilton 2015 Principal Investigator; University of Maine, Orono

Collaborative Research: Glacier-Ocean Coupling In A Large East Greenland Fjord, Gordon S. Hamilton

University of Maine Office of Research and Sponsored Programs: Grant Reports

This award will support a study of glacier-fjord interactions in east Greenland. The 'Intellectual Merit' of the proposed study lies in the current understanding that the contribution of the Greenland Ice Sheet to sea level rise more than doubled in the last seven years, mostly because of a widespread and nearly simultaneous acceleration of many glaciers that terminate at tidewater in deep fjords. Understanding the causes of changes in glacier dynamics, and predicting their future trajectories is a topic of enormous scientific and societal importance. The Greenland fjords provide an intimate connection between the ice sheet and the ocean and ...


Experimental Determination Of A Double-Valued Drag Relationship For Glacier Sliding, Lucas K. Zoet, Neal R. Iverson 2015 Iowa State University

Experimental Determination Of A Double-Valued Drag Relationship For Glacier Sliding, Lucas K. Zoet, Neal R. Iverson

Geological and Atmospheric Sciences Publications

The contribution of glaciers to sea-level rise and their effects on landscape evolution depend on the poorly known relationship between sliding speed and drag at the ice/bed interface. Results from experiments with a new rotary laboratory device demonstrate empirically for the first time a double-valued drag relationship like that suggested by some sliding theories: steady drag on a rigid, sinusoidal bed increases, peaks and declines at progressively higher sliding speeds due to growth of cavities in the lee sides of bed undulations. Drag decreases with increased sliding speed if cavities extend beyond the inflection points of up-glacier facing surfaces ...


Glacier Status And Contribution To Streamflow In The Olympic Mountains, Usa, Jon L. Riedel, Steve Wilson, William Baccus, Michael Larrabee, T.J. Fudge, Andrew G. Fountain 2015 National Park Service

Glacier Status And Contribution To Streamflow In The Olympic Mountains, Usa, Jon L. Riedel, Steve Wilson, William Baccus, Michael Larrabee, T.J. Fudge, Andrew G. Fountain

Geology Faculty Publications and Presentations

The Olympic Peninsula, Washington, USA, currently holds 184 alpine glaciers larger than 0.01 km² and their combined area is 30.2 ± 0.95km². Only four glaciers are >1km² and 120 of the others are -¹ (1900–80) to 0.54 km² a-¹ (1980–2009). Thinning rates on four of the largest glaciers averaged nearly 1ma-¹ from 1987 to 2010, resulting in estimated volume losses of 17–24%. Combined glacial snow, firn and ice melt in the Hoh watershed is in the range 63–79 ± 7 × 106m3, or 9–15% of total May–September streamflow ...


Geologic Map Of The Welcome Quadrangle And An Adjacent Part Of The Wells Quadrangle, Elko County, Nevada, Allen J. McGrew, Arthur W. Snoke 2015 University of Dayton

Geologic Map Of The Welcome Quadrangle And An Adjacent Part Of The Wells Quadrangle, Elko County, Nevada, Allen J. Mcgrew, Arthur W. Snoke

Geology Faculty Publications

Located in central Elko County, the Welcome and adjacent part of the Wells quadrangles expose a remarkable array of critical relationships for understanding the geologic history of the State of Nevada and the interior of the southwestern U.S. Cordillera. Covering the northern end of the East Humboldt Range and adjacent Clover Valley and Clover Hill, this map includes the northern terminus of the Ruby Mountains-East Humboldt Range metamorphic core complex. The oldest rocks in the State of Nevada (the gneiss complex of Angel Lake), and Nevada’s only exposures of Archean rock, form the core of a multikilometer scale ...


Contributing Factors To Ice Mass Loss On Himalayan Debris-Covered Glaciers, Ulyana Nadia Horodyskyj 2015 University of Colorado Boulder

Contributing Factors To Ice Mass Loss On Himalayan Debris-Covered Glaciers, Ulyana Nadia Horodyskyj

Geological Sciences Graduate Theses & Dissertations

Despite being heavily covered in debris, glaciers of the Himalaya have undergone and continue to undergo major losses of ice volume. This occurs not so much by loss of area, but more from a reduction in the thickness of the glacier at average rates that locally can exceed 1 m/year. This dissertation makes use of cartographic, photographic, and field data from the Tibetan Plateau and Ngozumpa, one of Nepal's largest and longest glaciers, towards determining and quantifying factors that influence glacial ice loss in the high Himalaya.

Volume estimates, using historical maps and archival/modern-day expedition photos, show ...


On The Uncertainty Of Sea-Ice Isostasy, Cathleen Geiger, Peter Wadhams, Hans-Reinhard Müller, Jacqueline Richter-Menge 2015 University of Delaware

On The Uncertainty Of Sea-Ice Isostasy, Cathleen Geiger, Peter Wadhams, Hans-Reinhard Müller, Jacqueline Richter-Menge

Open Dartmouth: Faculty Open Access Articles

During late winter 2007, coincident measurements of sea ice were collected using various sensors at an ice camp in the Beaufort Sea, Canadian Arctic. Analysis of the archived data provides new insight into sea-ice isostasy and its related R-factor through case studies at three scales using different combinations of snow and ice thickness components. At the smallest scale (<1 m; point scale), isostasy is not expected, so we calculate a residual and define this as 􏰀 (‘zjey’) to describe vertical displacement due to deformation. From 1 to 10 m length scales, we explore traditional isostasy and identify a specific sequence of thickness calculations which minimize freeboard and elevation uncertainty. An effective solution exists when the R-factor is allowed to vary: ranging from 2 to 12, with mean of 5.17, mode of 5.88 and skewed distribution. At regional scales, underwater, airborne and spaceborne platforms are always missing thickness variables from either above or below sea level. For such situations, realistic agreement is found by applying small-scale skewed ranges for the R-factor. These findings encourage a broader isostasy solution as a function of potential energy and length scale. Overall, results add insight to data collection strategies and metadata characteristics of different thickness products.


Changes In The Geometry And Volume Of Rabots Glaciär, Sweden, 2003-2011: Recent Accelerated Volume Loss Linked To More Negative Summer Balances, Keith A. Brugger, Latysha Pankratz 2015 University of Minnesota, Morris

Changes In The Geometry And Volume Of Rabots Glaciär, Sweden, 2003-2011: Recent Accelerated Volume Loss Linked To More Negative Summer Balances, Keith A. Brugger, Latysha Pankratz

Geology Publications

Terminus geometry, ice margins, and surface elevations on Rabots glaciär were measured using differential GPS during summer 2011 and compared with those similarly measured in 2003. Glacier length over the eight years decreased by ∼105 m corresponding to 13 m a−1, a rate consistent with ice recession over the last several decades. Measured changes in surface elevations show that between 2003 and 2011 the glacier’s volume decreased by ∼27.6 ± 2.6 × 106 m3, or 3.5± 0.3 × 106 m3 a−1. This compares favorably with an estimate of −28.1 ± 2.6 × 106 m3 based on ...


Patterns And Processes Of Salt Efflorescences In The Mcmurdo Region, Antarctica, Kelsey M. Bisson, Kathleen A. Welch, Susan A. Welch, Julia Meyer Sheets, W. Berry Lyons, Joseph S. Levy, Andrew G. Fountain 2015 Ohio State University

Patterns And Processes Of Salt Efflorescences In The Mcmurdo Region, Antarctica, Kelsey M. Bisson, Kathleen A. Welch, Susan A. Welch, Julia Meyer Sheets, W. Berry Lyons, Joseph S. Levy, Andrew G. Fountain

Geology Faculty Publications and Presentations

Evaporite salts are abundant around the McMurdo region, Antarctica (~78°S) due to very low precipitation, low relative humidity, and limited overland flow. Hygroscopic salts in the McMurdo Dry Valleys (MDVs) are preferentially formed in locations where liquid water is present in the austral summer, including along ephemeral streams, ice-covered lake boundaries, or shallow groundwater tracks. In this study, we collected salts from the Miers, Garwood, and Taylor Valleys on the Antarctic continent, as well as around McMurdo Station on Ross Island in close proximity to water sources with the goal of understanding salt geochemistry in relationship to the hydrology ...


Temporal Evolution Of Basal Water Pressure And Ice Velocity Along A 50 Km Flow Line Transect Of Western Greenland, Patrick Wright 2015 University of Montana - Missoula

Temporal Evolution Of Basal Water Pressure And Ice Velocity Along A 50 Km Flow Line Transect Of Western Greenland, Patrick Wright

Graduate Student Theses, Dissertations, & Professional Papers

The gradient in hydraulic potential at the ice-bedrock interface beneath the Greenland Ice Sheet (GrIS) dictates the routing and energetics of subglacial water, thereby influencing drainage system characteristics and sliding dynamics. In the ablation zone of the GrIS, a high relief bed and gradients in water pressure in an active subglacial drainage system potentially play a complex role in dictating the hydraulic potential field. Here we present a suite of water pressure measurements collected within thirteen boreholes along a 46 km transect on the western GrIS in order to investigate the sensitivity of the potential gradient field to seasonal evolution ...


Spring Thaw Ionic Pulses Boost Nutrient Availability And Microbial Growth In Entombed Antarctic Dry Valley Cryoconite Holes, Jon Telling, Alexandre M. Anesio, Martyn Tranter, Andrew G. Fountain, Thomas H. Nylen, Jon Hawkings, Virendra B. Singh, Preeti Kaur, Michaela Musilova, Jemma L. Wadham 2014 University of Bristol

Spring Thaw Ionic Pulses Boost Nutrient Availability And Microbial Growth In Entombed Antarctic Dry Valley Cryoconite Holes, Jon Telling, Alexandre M. Anesio, Martyn Tranter, Andrew G. Fountain, Thomas H. Nylen, Jon Hawkings, Virendra B. Singh, Preeti Kaur, Michaela Musilova, Jemma L. Wadham

Geology Faculty Publications and Presentations

The seasonal melting of ice entombed cryoconite holes on McMurdo Dry Valley glaciers provides oases for life in the harsh environmental conditions of the polar desert where surface air temperatures only occasionally exceed 0°C during the Austral summer. Here we follow temporal changes in cryoconite hole biogeochemistry on Canada Glacier from fully frozen conditions through the initial stages of spring thaw toward fully melted holes. The cryoconite holes had a mean isolation age from the glacial drainage system of 3.4 years, with an increasing mass of aqueous nutrients (dissolved organic carbon, total nitrogen, total phosphorus) with longer isolation ...


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